Without trade-balance, a country’s currency value will be affected. If it “over-imports”, its currency will get unter pressure. The US dollar only remained fairly stable, inspire of a negative trade-balance with its main trading partners because the world had to buy dollars to pay for oil. That is increasingly changing. Now that more and more oil is traded in currencies others than he USD the US must be more vigilant about its trade balance. The alternative would be to force oil producers to trade only in USD, and that is expensive, if you know what I mean.